An idealized model study into the effects of patchy vegetation on mean river flow

Introduction A paradigm shift in Dutch river management has lead to a focus on restoring natural rivers as a means of flood defence. This was initiated by a combination of changing European Union environmental policy and the realization that Dutch water management was subjected to a technological lock-in (Wesselink, 2007). The changes in river management have led to larger floodplain dimensions and more frequent inundations. As a result, more research focuses on the flow processes over these floodplains, and how these influence discharge capacity. Herein the modelling of hydraulic roughness, specifically as caused by vegetation rather than bedforms, is of key importance for changing water levels due to resistance. Recent research has shown that a change of 50% in roughness can lead to a 40% change in peak water level (Ballesteros et al., 2011).